Stirred fluid-bed dryers

ABSTRACT

A direct-heat-stirred fluid-bed dryer for fluidizing continuously changing portions of a slurry or other moist product to be dried while stirring the product and applying sonic energy to the product for efficient dehydration.

United States atent [72] lnventors Raymond M. Lockwood Los Altos; David A. Graber, Menlo Park, both of, Calif.

[21] Appl. No. 759,959

[22] Filed Sept. 16, 1968 [45] Patented July 13, 1971 [73] Assignee International Dehydrating Corporation Fullerton, Calif.

[54] STIRRED FLUID-BED DRYERS 1,157,935 10/1915 Gray 34/57 R 1,634,480 7/1927 Wickenden et a1... 34/57 R 2,070,235 2/1937 Mullen 263/21 A X 2,761,769 9/1956 Elder r 34/57 R X 2,841,384 7/1958 Petersen 34/57 R X 2,950,592 8/1960 Frank 431/1 X 2,974,419 3/1961 Hauk et al. 34/57AX 3,192,644 7/1965 Knibbs et a1... 263/21 A X 3,236,509 2/1966 B1air........ 263/21 A 3,298,792 1/1967 DiDrusco 34/57 A X FOREIGN PATENTS 1,273,700 9/1961 France 34/57 A Primary Examiner- Frederick L. Matteson Assistant Examiner-Robert A. Dua Attorney- Harris, Kiech,Russell & Kern ABSTRACT: A direct-heat-stirred fluid-bed dryer for fluidizing continuously changing portions of a slurry or other moist product to be dried while stirring the product and applying sonic energy to the product for efficient dehydration.

PATENTEB JUL] 3191] 592. 3595 saw 1 0F 2 INVENTORS 24 RAYMOND M. LOCKWOOD 3 (gm, 45 46 BY DAVID A. GRABER W A -2 ATTORNEYS PATENIEflJuusmn SHEET 2 BF 2 3,592,395

U V v a V 3 V 5 A, V A, V A, iL R V 5 ATTORNEYS STIRRED FLUID-BED DRYERS This invention relates to a new and improved direct-heatstirred fluid-bed dryer for dehydrating a slurry or other moist product into a dried, granular or mealy form and for sterilizing the product.

Typical fluid-bed dryers introduce drying gases into the drying tank or chamber through a porous or perforated grid and into the material to be dried in order to distribute the drying gases introduced under pressure to maintain a fluidized bed of the material. A problem with such conventional fluid-bed dryers is that the temperature of the perforated grid or distributor plate through which the hot gases enter rises to a point at which slurry-type products stick to the grid or distributor plate.

It is an object of the present invention to provide a new and improved direct heat fluid-bed dryer having lower effective wall and floor temperatures to thereby reduce the tendency of a slurry or moist product to stick to the floor and walls of the dryer and become overheated causing product damage and smoke nuisance. It is also an object of the invention to maintain a high rate of heat transfer by fluidization of slurry-type products to be dried without buildup of the dried product on the floor and inside surfaces of the dryer. Fluidization as used herein refers to suspension and agitation of material by a stream of gas.

Another object of the invention is to provide a direct heat fluid-bed dryer in which the product is subjected to a mild stirring, which imparts turbulence to the processing material, in combination with a fluidized-type direct gas-to-heat material heat transfer. According to the invention slurry-type products can be fluidized by fluidizing continuously changing portions of the slurry. The invention is thus particularly suitable for processing sticky feed material and slurries to a granular or mealy dried end product.

A further object of the invention is to provide a pulsed jet of hot gases and a broad spectrum of acoustical energy to the processing material in a direct heat fluid-bed dryer to increase the efflciency and rate of drying. A feature of the invention is that one or more pulse jet combustion engines are utilized as heat blowers in the dryer.

Yet another object of the invention is to provide a direct heat fluid-bed dryer in which oil and similar liquids are rendered from the product by melting and then removed from the dryer tank.

According to the method of drying contemplated by the present invention, the product to be dried is first ground into a slurry-type material. This material is then dehydrated by fluidizing continuously changing sections of the slurry-type material while stirring the material.

In order to accomplish these results the present invention contemplates providing a dryer tank having cylindrical walls, a top cover portion tapering to a gas outlet, and a bottom floor having a centrally located gas inlet. A plurality of flat stirring blades radially extending from a hub are mounted centrally in the tank for rotation inside the tank adjacent the floor of the tank. The hub is positioned over the gas inlet centrally located in the floor of the tank. Each stirring blade is sloped in the direction of rotation to provide a leading edge for scraping and receiving the product retained in the tank and a raised trailing edge spaced from the floor of the tank adapted for passing the product over the trailing edge of the blade. A gas conduit provides a passageway from the gas inlet through the central hub to the under surface of each of the stirring blades.

The invention also contemplates providing one or more pulse jet combustors as heat blowers at the gas inlet to supply hot gas under pressure and a broad spectrum of acoustical energy. The hot gas pulses under pressure pass through the gas conduit to the under surface of the blades and out the trailing edge of the blades as the blades are rotated at a controlled rate. I-Iot gas thus passes directly through the product retained within the tank as it passes over the trailing edge of each blade. Sonic energy increases the efficiency of dehydration.

Conventional heater blowers can also be used for supplying hot gases.

A feature and advantage-of the invention is that the large surface area of the stirring blades and the floor and sidewalls of the dryer are colled rapidly by continuous contact with the slurry or moist product retained in the tank so that the heatis dissipated in removing moisture from the slurry or product without sticking of the material on the floor and inside surfaces of the dryer.

Another feature of the invention is that the shape and relative motion of the blades is controlled to impart turbulence, to the processed material in the bed to aid in the transition of the. slurry or other moist product to a dried end product. Accord,-

ing to the invention the gas pressure and velocity are adjusted.

to fluidize continuously changing radial sections fromthe product retained in the dryer tank passing over the trailing edge of each, stirring blade. The dryer tank is also provided with inlets for continuously introducing the product to be dried and continuously withdrawing the dried product. Stator and rotor scraperbars are provided in conjunction with the stirring blades to provide efficient stirring and circulation of the processed material.

According to another embodiment of the invention, the cylindrical wall of the tank is formed with small holes or perforations around the bottom of the wall and/or sections of the floor. An oil-collecting ring is provided around and beneath the perforated portion of the cylindrical wall to collect oils and liquids melted by the hot gas passing through the perforations. Hot gas under slight pressure in the tank facilitates. passage of oil and. melted liquids through the perforations.

The invention also contemplates the use of pulse jet engines as hot gas jet pumps for conventional fluid-bed, dryers to pro vide pulsed jets of hot gas and acoustical energy to increase the rate of drying, reduce clogging of the system, and increase the material processing rate while providing simpler construction than heretofore used in conventional fluidbed dryers.

Other objects, features and advantages of the present invention will become apparent in the following specification and accompanying claims.

FIG. I is a diagrammatic cross-sectional view of a directheat-stirred fluid-bed dryer embodying the present invention.

FIG. 2 is a cross-sectional plan view of the dryer tank in the direction of the arrows on line 2-2 of FIG. 1.

FIG. 3 is a fragmentary cross-sectional view of a blade, stator bar and rotor bar adjacent the floor of the dryer tank in the direction of the arrows on line 3-3 of FIG. 2.

FIG. 4 is a diagrammatic view in side cross section of another dryer embodying the present invention.

FIG. 5 is a cross-sectional plan view of the dryer tank in the direction of the arrows on line 5-5 of FIG. 4.

In the embodiment of the present invention illustrated in FIGS. 1 through 3 there is shown a direct-heat-stirred fluidbed dryer having a dryer tank 10 formed by cylindrical walls 11, a conical cover 12 tapering to a gas outlet 13, and a solid floor or bottom wall 14 having a centrally located gas inlet 15.

A plurality of flat stirring blades 20 radially extending from a hub 21 are mounted centrally in the tank 10 adjacent the floor of the tank. The blades and hub are mounted for rotation inside the tank on a shaft 22 with the hub positioned over the gas inlet 15 formed centrally in the floor of the tank. Flat plate 210 in the hub 21 deflects gas from the inlet to the undersurface of the stirring blades. The shaft 22 and a motor, not shown, provide rotation of the stirring blades at a controlled rate. Each stirring blade is sloped in the direction of rotation to provide a leading edge 23 for scraping and receiving the slurry or moist product retained in the tank, the product passing along the upper surface of the blade. Each blade is also provided with a raised trailing edge 24 spaced from the floor of the tank so that the product passes over the trailing edge of the blade during rotation. The gas inlet 15 and hollow hub 21 provide a gas conduit for directing gas received at the inlet 15 radially outward along the under surface of the stirring blades 20.

The hot drying gas is provided by valveless pulse jet combustors 30 and 31 positioned to direct pulses of hot gas through augmentors 32 and 33 into the gas inlet 15. Such pulse jet combustors provide a wide spectrum of sonic energy, transmitted to the slurry or product through the air, which promotes efficient dehydration. I-lot gas pulse jet pumps of the type used herein are described in A.I.A.A. Paper No. 64- l 72 by R. M. Lockwood entitled Pulse-Reactor Low Cost Lift- Propulsion Engines" and dated May, 1964. This paper may be obtained from the American Institute of Aeronautics and Astronautics, 1290 Sixth Avenue, New York, New York 10019. Such a pulse jet engine or pulse reactor includes a combustion chamber 34, and a pair of exhausts which are referred to as the inlet 35 and the tail pipe 36. The combustion chamber 34 includes a passageway for receiving air/fuel mixtures and a spark for sparking the initial air/fuel mixture received in the combustion chamber. As combustion occurs the pressure buildup forces hot gas out both ends of the combustor, that is, from the inlet as well as from the tailpipe. Over expansion occurs producing a low-pressure area in the combustion chamber 34 which draws in another air/fuel mixture and also draws back hot gas from the tailpipe which reignites the new air/fuel mixture to produce multiple points of ignition, and another combustion and expansion. The cycle then proceeds indefinitely without moving parts. The augmentors 32 and 33 significantly increase the thrust from the engine exhaust. Instead of a pair of pulse jet combustors a single pulse jet combustor or reactor may be utilized with a 180 bend in the tailpipe to redirect it toward the other augmentor. Valved pulse jet engines can also be used. In such pulse jet engines one or more valves are included at the inlet end of the combustor. In the embodiment of the present invention shown in FIG. 1, the pair of pulse jet reactors 30 and 31 can be used to drive a second dryer from the unused exhaust ends of the two reactors.

Instead of the pulse jet type combustors, a conventional steady hot gas jet source can be used with the dryer described above. However, because of the pulses in the hot gas stream and the acoustical energy provided by pulse jet combustors, such combustors result in an increase in the rate of drying by a factor of2 to 10.

Hot gas pumped by the pulse jet reactors passes through the inlet 15 and hub 21 along the under surface of the blades 20 and is expelled out the trailing edge of each of the blades to pass through the slurry or moist product retained within the tank as it passes over the trailing edge of each of the blades. The moisture-filled gas then passes out the gas outlet 13. Dried product also passes out with the gas and can be separated in an air particle separator such as a cyclone, baffle system, bag separator etc.

The moist product or slurry is continuously passed into the tank through an inlet 40 by means of an auger or pump to pass over the hub 21 and be distributed evenly about the tank. As the product 41 is dried the courser and heavier particles are continuously withdrawn through an outlet 42 in the side of the tank. In certain applications it may be advantageous to introduce the slurry or other moist product into the tank at another point than over the hub such as from the side or from another point as is known in the art.

The flat stirring blades 20 may be formed in a variety of configurations to provide a leading edge for scraping and lifting the product and a raised trailing edge over which the product passes. As shown in FIG. 3, the stirring blade of the illustrated embodiment is formed by a planar sheet folded along a radial line extending from the center of the tank. Other cross-sectional shapes for the stirring blades such as a straight line or a curved line can also be used. As the blade rotates turbulence is imparted to the product passing over the surface of the blade. A plurality of stator bars 45 are positioned around the tank extending radially from the center of the tank to the cylindrical wall. The stator scraper bars 45 are maintained in a stationary position with respect to the dryer tank walls. As each of the blades passes under a stator scraper bar 45, the

material passing along the upper surface of the stirring blade is scraped off so that it passes over the raised trailing edge to be exposed to the hot gases venting from beneath the trailing edge. There are also provided a plurality of rotor scraper bars 46 extending around the tank radially from the central axis, one rotor bar for each blade. The rotor bars are linked with the hub 21 so that they rotate with the stirring blades. The rotor scraper bars 46 are positioned immediately above the stator scraper bars so that any material collecting on the stator bars is scraped off by the rotor bars. Other combinations of rotor bars and stator bars can also be used to increase stirring efficiency. Furthermore, it is also advantageous to connect the stationary stator scraper bars to the tank wall and at an angle of for example 10from the radius of the tank so that the stator sweeps the rotating blade in a scissorlike fashion continuously pushing material in the tank back towards the hub. The stators so angled tend to maintain a somewhat deeper bed at the hub forcing hot gases toward the tips of the rotating blades. This reduces blowout of gases near the hub.

In the method of drying contemplated by the present invention, the product to be dried is first ground into a slurry, granular or finely divided solid, or other pulverized form. Grinding can be accomplished by extruding the product through, for example, a 3/l6-inch or l/4-inch-mesh grid plate. Grinding permits fluidization of the resulting slurry or pulverized material for efficient drying. However, fluidization of slurry-type material has hereto been unsuccessful. According to the present invention this is accomplished by fluidizing continuously changing sections of the slurry bed while stirring the slurry. Sonic energy is also applied to promote rapid dehydration.

In practicing the invention it is advantageous to first place a layer of already dried material at the bottom of the dryer tank before introducing the ground slurry or other pulverized moist material. This step permits operation of the stirring blades in a dried bed environment so that high initial starting power is not required.

It is apparent that dryers other than that described above can be used in practicing this method of drying. For example, instead of rotating the stirring blades through the slurry, stirring blades of the type described above can be arranged in a row and passed through the slurry in a conveyor-type manner with suitable gas conduits for passing hot gas out the trailing edge ofeach stirring blade. 7

According to the embodiment of the present invention illustrated in FIGS. 4 and 5 there is provided a dryer tank 50 similar to that illustrated in FIGS. 1 and 2. The dryer tank includes a cylindrical wall 51 and a conical cover 52 tapering to a gas outlet 53. A floor 54 of the tank includes a gas inlet 55 positioned centrally in the floor. A plurality of stirring blades 56 radially extending from a hub 57 are mounted for rotation inside the tank adjacent the floor of the tank with the hub 57 positioned over the gas inlet 55. A central shaft 58 is provided for imparting rotation at a controlled rate to the stirring blades. Stator scraper bars 60 and rotor scraper bars 61 as heretofore described are also provided. The slurry, moist product or raw material to be processed is fed through an inlet 62 y means f an auger or other means so that it is distributed evenly about the hub 57 and into the tank. An outlet 63 is used for continuously withdrawing processed material.

Around the lower portion of the cylindrical wall 51 small holes or perforations 65 are formed to permit oil and similar liquids to be melted by the hot gas and removed from the product through the holes or perforations. The slightly higher gas pressure in the tank aids in passing oils and other melted liquids through the holes. Oil collected by the oil collector ring 67 passes out the oil outlet 68 from the oil collector ring.

In addition to or instead of the perforations formed in the lower part of the cylindrical wall, small holes can also be formed in the bottom of the dryer tank. Perforations can be made through any lower portions of the dryer tank in the form of small holes, slits and other configurations. Holes in the bottom of the tank can be arranged in a variety of positions with suitable reservoirs or conduits below for removal of rendered oils.

In each of the embodiments of the invention described above, the floor of the dryer tank need not be flat but can be, for example, conical in shape, the floor sloping upwards from the hub so that the bed of material is deeper near the hub. Furthermore, in certain applications it is desirable to vary the height of the trailing edge of the blades above the dryer floor. With the blade lower near the hub and higher near the tip, the flow of air from beneath the blade near the hub is reduced. increasing the flow of hot gases toward the wall of the dryer.

Pulse jet combustors of the type referred to herein can also be applied with advantage to fluid-bed dryers of the conventional type. Thus, by means of the pulse jet hot gas pumps, 21 fluid bed over a conventional hot gas distributing grid plate can be better maintained and supported with less sticking of material on the grid plate. Furthermore, the broad spectrum of sonic energy applied to the material by pulse jet combustion engines increases the efficiency and rate of drying.

The present invention is applicable not only for dehydrating slurry-type materials but also for drying other moist products such as granular or finely divided solids and for sterilizing such products.

What we claim is:

l. A method of dehydrating products comprising: grinding the product to be dried into a pulverized material; fluidizing continuously changing sections of the pulverized material while stirring the material; applying a hot pulsating sonic gas as the fluidizing and drying medium upward from beneath the pulverized material during the dehydration process; and continuously removing dried pulverized material from the top of the fluidized material.

'2. A method of dehydrating products comprising: placing a layer of a portion of ground dehydrated product in the bottom of a dryer tank; grinding another portion of the not as yet dehydrated product into a pulverized form; passing the pulverized product into the dryer tank over the layer of ground already dehydrated product; stirring both portions of the product in the tank; fluidizing continuously changing sections of both portions of the product while stirring the product and passing hot sonic pulsating gas as the fluidizing and drying medium upward from beneath the product; and continuously removing dried pulverized material from the top of the fluidized product.

3. A method of dehydrating products comprising: grinding the product to be dried into a pulverized material; placing the material in a supporting bed; stirring the material by scraping the material from the supporting bed, raising the material, and dropping the material back into the bed; blowing hot sonic pulsating gas out from beneath the raised material thereby fluidizing the portions of the raised material dropping back into the supporting bed; continuously removing the dehydrated product from the top of said stirred and fluidized material; and continuously adding ground product to said stirred and fluidized material.

4. The method according to claim 3 wherein said material is stirred with rotating blades situated adjacent the bottom of the dryer tank, and said hot sonic pulsating gas is passed out the tailing edge of said blades and upward through the product to dehydrate said product.

5 A dryer tank having a cylindrical wall with a top closure and a bottom closure, said top closure tapering to a first outlet, said bottom closure having a centrally located first inlet, said closures and wall formed to retain a product to be dried; a hub positioned over said first inlet-located in the floor of the tank; a plurality of stirring blades radially extending from said hub, each said blade mounted for rotation closely adjacent the floor of the tank, each said stirring blade sloped in the direction of rotation to provide a leading edge for scraping and receiving product retained in the tank and passing the product along the top of the blade, and a raised trailing edge spaced further than the leading edge from the bottom closure of the tank to form a gas manifold area under each blade extending the length of the blade, with a discharge outlet formed by the bottom closure of the tank and the trailing edge of each blade; gas conduit means formed to conductgas from the first inletto the gas manifold area under said stirring blades; means for rotating said hub at a controlled rate; and a pressurized hot gas source constructedand arranged to supply hot gas under pressure to the first inlet; said dryer tank formed with a second inlet for introducing product to be dried and a second outlet for withdrawing product dried within the tank.

6. A stirred-bed, direct-heat dryer as set forth in claim 5 wherein the gas pressure and velocity from said hot gas source is adjusted to fluidize portions of the product retained in the dryer tank and passing over the trailing edge of each stirring blade.

7. A dryer as set forth in claim 5 wherein said hot gas source comprises'at least one pulse jet engine.

8. A stirred-bed, direct-heat dryer as set forth in claim 5 wherein at least one stationary stator scraper bar is provided extending from the cylindrical wall of the tank above the rotating stirring blades whereby product is scraped ofi the upper surface and over the trailing edge of each stirring blade as it passes beneath the stator scraper bar.

9. A stirred-bed, direct-heat dryer as set forth in claim 8 wherein said stationary stator scraper bar is positioned at an angle with respect to the radius of the dryer tank.

10. A stirred-bed, direct-heat dryer as set forth in claim 8 wherein at least one rotor scraper bar is provided, positioned extending radially from the center of the tank to pass above the stator scraper bar to scrape product off of the stator scraper bar.

11. A stirred-bed, direct-heat dryer as set forth in claim 5 wherein the height of the trailing edge of said blade from the floor of the dryer tank increases in the direction from the hub to the cylindrical wall.

12. A stirred-bed, direct-heat dryer as set forth in claim 5 wherein the tank is formed with holes through lower portions of the tank, and wherein there is provided an oil conduit beneath the holes in the tank formed to collect liquids passing through the holes.

13. A stirred-bed, direct-heat dryer as set forth in claim 5 wherein the bottom floor of said dryer tank is conical in shape.

14. A stirred-bed, direct-heat dryer comprising: a dryer tank having cylindrical walls, a cover portion, gas outlet means, and a bottom floor having a centrally located gas inlet, said dryer tank formed with holes therethrough in the lower portion of the tank; a hub and a plurality of flat stirring blades radially extending from the hub, said hub mounted centrally in the tank over said gas inlet located in the floor of the tank, said blades mounted for rotation inside the tank adjacent the floor of the tank, each said stirring blade sloped in the direction of rotation to provide a leading edge for scraping and receiving product retained in the tank and passing the product along the top of the blade, and a raised trailing edge spaced from the floor of the tank for passing product over the trailing edge of the blade; an oil conduit formed beneath the holes through the dryer tank to collect liquids passing through the holes; gas conduit means formed to conduct gas from the gas inlet to the undersurface of said stirring blades; means for rotating said blades at a controlled rate; hot gas jet means positioned to supply hot gas under pressure to the gas inlet whereby hot gas passes through said gas conduit means, out the trailing edge of said blades, and through product retained within the tank passing over the trailing edge of each blade.

15. A stirred-bed, direct-heat dryer comprising: a dryer tank having cylindrical walls, a top cover portion, gas outlet means,

and a bottom floor having a centrally located gas inlet, said floor and walls adapted for retaining a product to be dried; a hub and a plurality of flat stirring blades radially extending from the hub, said hub mounted centrally in the tank over said gas inlet located in the floor of the tank, said blades mounted for rotation inside the tank adjacent the floor of the tank, each said stirring blade sloped in the direction of rotation to provide a leading edge for scraping and receiving product retained in the tank and passing the product along the top of the blade, and a raised trailing edge spaced from the floor of the tank for passing product over the trailing edge of the blade; gas conduit means formed to conduct gas from the gas inlet to the undersurface of said stirring blades; means for rotating said blades at a controlled rate; product inlet means for introducing product to be dried into the dryer tank; hot gas jet means comprising at least one pulse jet combustor positioned to supply acoustical energy to product retained in the dryer tank and pulsed jets of hot gas under pressure to the gas inlet whereby hot gas passes through said conduit means, out the trailing edge of said blades and through product retained within the tank passing over the trailing edge of each blade.

16. A stirred-bed direct-heat dryer as set forth in claim wherein said pulse jet combustor is a valveless pulse jet combustor.

17. A stirred-bed, direct-heat dryer as set forth in claim 15 wherein the velocity and pressure of the hot gas jets are adjusted to entrain and fluidize product passing over the trailing edge of each blade.

18. A dryer comprising a tank having a bottom wall, a rotating element mounted in said tank for movement adjacent said bottom wall having a leading edge spaced in immediate proximity to the bottom wall and a trailing edge spaced a distance from said bottom wall greater than said leading edge, and means for supplying hot gas to said element in the area between the element and the bottom of the tank whereby the flow of the hot gas into the tank exists from beneath the trailing edge of the element.

19. A dryer according to claim 18 wherein a foraminous cylinder is formed around said element and said element is mounted for rotation coaxially within said foraminous cylinder, and wherein there is provided around said foraminous cylinder a liquid-capturing canal, and means for withdrawing liquid from said canal.

20. A liquid-solid phase classifying dryer comprising a tank, a cylindrical bed formed in said tank having at least a portion of the wall of said tank formed of foraminous material, a blade rotatably mounted within said bed coaxially of the sidewalls to said bed, a liquid canal formed in fluid communication with the foraminous section of said wall, means supplying hot gas to materials within said bed, means for withdrawing solid materials from the top portion of said bed, and means for withdrawing fluid material from said canal. 

2. A method of dehydrating products comprising: placing a layer of a portion of ground dehydrated product in the bottom of a dryer tank; grinding another portion of the not as yet dehydrated product into a pulverized form; passing the pulverized product into the dryer tank over the layer of ground already dehydrated product; stirring both portions of the product in the tank; fluidizing continuously changing sections of both portions of the product while stirring the product and passing hot sonic pulsating gas as the fluidizing and drying medium upward from beneath the product; and continuously removing dried pulverized material from the top of the fluidized product.
 3. A method of dehydrating products comprising: grinding the product to be dried into a pulverized material; placing the material in a supporting bed; stirring the material by scraping the material from the supporting bed, raising the material, and dropping the material back into the bed; blowing hot sonic pulsating gas out from beneath the raised material thereby fluidizing the portions of the raised material dropping back into the supporting bed; continuously removing the dehydrated product from the top of said stirred and fluidized material; and continuously adding ground product to said stirred and fluidized material.
 4. The method according to claim 3 wherein said material is stirred with rotating blades situated adjacent the bottom of the dryer tank, and said hot sonic pulsating gas is passed out the tailing edge of said blades and upward through the product to dehydrate said product.
 5. A dryer tank having a cylindrical wall with a top closure and a bottom closure, said top closure tapering to a first outlet, said bottom closure having a centrally located first inlet, said closures and wall formed to retain a product to be dried; a hub positioned over said first inlet located in the floor of the tank; a plurality of stirring blades radially extending from said hub, each said blade mounted for rotation closely adjacent the floor of the tank, each said stirring blade sloped in the direction of rotation to provide a leading edge for scraping and receiving product retained in the tank and passing the product along the top of the blade, and a raised trailing edge spaced further than the leading edge from the bottom closure of the tank to form a gas manifold area under each blade extending the length of the blade, with a discharge outlet formed by the bottom closure of the tank and the trailing edge of each blade; gas conduit means formed to conduct gas from the first inlet to the gas manifold area under said stirring blades; means for rotating said hub at a controlled rate; and a pressurized hot gas source constructed and arranged to supply hot gas under pressure to the first inlet; said dryer tank formed with a second inlet for introducing product to be dried and a second outlet for withdrawing product dried within the tank.
 6. A stirred-bed, direct-heat dryer as set forth in claim 5 wherein the gas pressure and velocity from said hot gas source is adjusted to fluidize portions of the product retained in the dryer tank and passing over the trailing edge of each stirring blade.
 7. A dryer as set forth in claim 5 wherein said hot gas source comprises at least one pulse jet engine.
 8. A stirred-bed, direct-heat dryer as set forth in claim 5 wherein at least one stationary stator scraper bar is provided extending from the cylindrical wall of the tank above the rotating stirring blades whereby product is scraped off the upper surface and over the trailing edge of each stirring blade as it passes beneath the stator scraper bar.
 9. A stirred-bed, direct-heat dryer as set forth in claim 8 wherein said stationary stator scraper bar is positioned At an angle with respect to the radius of the dryer tank.
 10. A stirred-bed, direct-heat dryer as set forth in claim 8 wherein at least one rotor scraper bar is provided, positioned extending radially from the center of the tank to pass above the stator scraper bar to scrape product off of the stator scraper bar.
 11. A stirred-bed, direct-heat dryer as set forth in claim 5 wherein the height of the trailing edge of said blade from the floor of the dryer tank increases in the direction from the hub to the cylindrical wall.
 12. A stirred-bed, direct-heat dryer as set forth in claim 5 wherein the tank is formed with holes through lower portions of the tank, and wherein there is provided an oil conduit beneath the holes in the tank formed to collect liquids passing through the holes.
 13. A stirred-bed, direct-heat dryer as set forth in claim 5 wherein the bottom floor of said dryer tank is conical in shape.
 14. A stirred-bed, direct-heat dryer comprising: a dryer tank having cylindrical walls, a cover portion, gas outlet means, and a bottom floor having a centrally located gas inlet, said dryer tank formed with holes therethrough in the lower portion of the tank; a hub and a plurality of flat stirring blades radially extending from the hub, said hub mounted centrally in the tank over said gas inlet located in the floor of the tank, said blades mounted for rotation inside the tank adjacent the floor of the tank, each said stirring blade sloped in the direction of rotation to provide a leading edge for scraping and receiving product retained in the tank and passing the product along the top of the blade, and a raised trailing edge spaced from the floor of the tank for passing product over the trailing edge of the blade; an oil conduit formed beneath the holes through the dryer tank to collect liquids passing through the holes; gas conduit means formed to conduct gas from the gas inlet to the undersurface of said stirring blades; means for rotating said blades at a controlled rate; hot gas jet means positioned to supply hot gas under pressure to the gas inlet whereby hot gas passes through said gas conduit means, out the trailing edge of said blades, and through product retained within the tank passing over the trailing edge of each blade.
 15. A stirred-bed, direct-heat dryer comprising: a dryer tank having cylindrical walls, a top cover portion, gas outlet means, and a bottom floor having a centrally located gas inlet, said floor and walls adapted for retaining a product to be dried; a hub and a plurality of flat stirring blades radially extending from the hub, said hub mounted centrally in the tank over said gas inlet located in the floor of the tank, said blades mounted for rotation inside the tank adjacent the floor of the tank, each said stirring blade sloped in the direction of rotation to provide a leading edge for scraping and receiving product retained in the tank and passing the product along the top of the blade, and a raised trailing edge spaced from the floor of the tank for passing product over the trailing edge of the blade; gas conduit means formed to conduct gas from the gas inlet to the undersurface of said stirring blades; means for rotating said blades at a controlled rate; product inlet means for introducing product to be dried into the dryer tank; hot gas jet means comprising at least one pulse jet combustor positioned to supply acoustical energy to product retained in the dryer tank and pulsed jets of hot gas under pressure to the gas inlet whereby hot gas passes through said conduit means, out the trailing edge of said blades and through product retained within the tank passing over the trailing edge of each blade.
 16. A stirred-bed direct-heat dryer as set forth in claim 15 wherein said pulse jet combustor is a valveless pulse jet combustor.
 17. A stirred-bed, direct-heat dryer as set forth in claim 15 wherein the velocity and pressure of the hot gas jets are adjusted to entrain and fluidize product passing over the trailing eDge of each blade.
 18. A dryer comprising a tank having a bottom wall, a rotating element mounted in said tank for movement adjacent said bottom wall having a leading edge spaced in immediate proximity to the bottom wall and a trailing edge spaced a distance from said bottom wall greater than said leading edge, and means for supplying hot gas to said element in the area between the element and the bottom of the tank whereby the flow of the hot gas into the tank exists from beneath the trailing edge of the element.
 19. A dryer according to claim 18 wherein a foraminous cylinder is formed around said element and said element is mounted for rotation coaxially within said foraminous cylinder, and wherein there is provided around said foraminous cylinder a liquid-capturing canal, and means for withdrawing liquid from said canal.
 20. A liquid-solid phase classifying dryer comprising a tank, a cylindrical bed formed in said tank having at least a portion of the wall of said tank formed of foraminous material, a blade rotatably mounted within said bed coaxially of the sidewalls to said bed, a liquid canal formed in fluid communication with the foraminous section of said wall, means supplying hot gas to materials within said bed, means for withdrawing solid materials from the top portion of said bed, and means for withdrawing fluid material from said canal. 